Functionalized ethylene-based polymers are ethylene-based polymers, e.g., homopolymers of ethylene such as high density polyethylene (HDPE), high pressure low density polyethylene (LDPE), etc., or copolymers of ethylene and one or more C3-C20 alpha olefins such as copolymers of ethylene and propylene, or 1-butene, or 1-hexene, or 1-octene, etc., with one or more functionalization agents, e.g., maleic anhydride (MAH), etc., bonded to the backbone of the ethylene-based polymer. One example of a commercially available functionalized ethylene-based polymer is the family of AMPLIFY™ GR functional polymers, e.g., maleic anhydride (MAH) grafted polyethylene (MAH-g-polyethylene).
In a typical preparation of a functionalized ethylene-based polymer, an ethylene-based polymer is contacted with a functionalization agent under grafting conditions. These conditions typically include the use of a free radical initiator, e.g., a peroxide or azo compound. These materials are typically contacted with one another at an elevated temperature in a reaction vessel such as an extruder. While effective, this process typically produces a final product of a functionalized ethylene-based polymer containing gels that are the result of crosslinking due to the premature activation of the free radical initiator. Ideally, the ethylene-based polymer, functionalization agent and free radical initiator are mixed with one another for an extended period of time to produce a homogenous reaction mass before the initiator is activated, but often at least some of the initiator is activated due to either the shear forces generated within the extruder or reaching the initiator activation temperature before a homogeneous reaction mass is obtained and this, in turn, allows the ethylene-based polymer to crosslink as opposed to react with the functionalization agent. Depending upon the nature and amount of gels in a functionalized ethylene-based polymer, the polymer may well be unsuited for its intended purpose.